The invention relates to an apparatus for making drawings, for example drawings on a sheet-like drawing carrier, such as a sheet of transparent paper, by means of a device for producing points, lines or the like, such as a pen or pencil or a pair of compasses, comprising a drawing surface of a board or the like, which temporarily accommodates the drawing carrier and which is variable in particular in respect of its inclination relative to a support surface, and which is provided with a drawing aid which is displaceable over its surface, in the form of a ruler or the like.
Such apparatuses have long been known in the form of drawing machines with an inclinable drawing board and rulers which are carried movably thereon. The latter are fixed for example to carriages which can slide along an edge of the board and which possibly themselves in turn guide templates or the like. Accessory equipment for such drawing machines are also high-speed drawing heads which are rotatable about an axis, comprising two ruler portions which are disposed at a right angle to each other.
The document `VDI-Nachrichten` of 13th Apr. 1990 expresses the view that `Computers are not yet replacing the drawing board`; investigation revealed serious deficiencies in regard to present CAD-systems, in particular weaknesses in terms of design, sketch drafting and data acquisition. Thus, in the case of complete redesigns, it is necessary to reckon on a clear additional expenditure of about 110% to 150%, in comparison with manual drafting.
Admittedly, the state of the art already includes digitizing systems with aiming devices which are movable on a bridge over the surface of the drawing board, such as magnifying glasses with a crosshair arrangement or the like, by virtue of which it is possible to go to points on a drawing and such points are passed by means of a digital transfer device to a computer for data acquisition.
However, with the so-called digitizers which are available on the market, it has been found that accurate drawing by hand (guiding a drawing pen or pencil or magnifying glass) is not possible, even with a ruler/template, in order reliably to hit the notional grid or pattern points with their tolerance zone (for example +/- 0.5 mm); for starting at the periphery of the tolerance zone results in slight overshoot or undershoot effects of for example 0.1 mm in relation to a line to be produced, so that it is not possible to get to the targeted point but the tolerance zone of the adjacent grid or pattern point is already affected. That then gives rise to a defective computer program input, which means that the described system is unusable for accurate technical drawings. Consequently, hitherto accurate inputs have been achieved only by virtue of co-ordinate point and/or distance information using a keyboard or a menu area on a table.
With knowledge of that state of the art, the inventor set himself the aim of improving the manual production of technical drawings and providing for that purpose support and conservation by means of data processing apparatus. The invention further seeks to simplify further work on intermediate plots, lettering and labelling, and the storage of data.